Generation of Trains of Electron Microbunches with Adjustable Subpicosecond Spacing

Abstract

We demonstrate that trains of subpicosecond electron microbunches, with subpicosecond spacing, can be produced by placing a mask in a region of the beam line where the beam transverse size is dominated by the correlated energy spread. We show that the number, length, and spacing of the microbunches can be controlled through the parameters of the beam and the mask. Such microbunch trains can be further compressed and accelerated and have applications to free electron lasers and plasma wakefield accelerators.

Hollow plasma channel for positron plasma wakefield acceleration

“…As way of background, it has been demonstrated in experiments that when propagating in uniform plasmas, e þ beams drive smaller amplitude wakefields than e À beams with similar parameters [13]. It was also observed that these positron beams develop a charge halo [14]. As expected, numerical simulations show that the nonlinear plasma focusing force creating the halo also leads to emittance growth [14].…”

“…It was also observed that these positron beams develop a charge halo [14]. As expected, numerical simulations show that the nonlinear plasma focusing force creating the halo also leads to emittance growth [14]. However, simulations also indicate that larger gradients can be driven in hollow plasma channels than in uniform plasmas [6].…”

“…A DB/WB train can be produced using a masking technique recently demonstrated [14]. The effect of the plasma channel radius on the peak accelerating gradient driven by the DB, as well as on the transformer ratio was calculated.…”

Terahertz radiation source based on self-wake beam bunching

“…This method is simple, but yields wide band THz radiation. This method in fact is used in CTR (coherent transition radiation) interferometry to determine the bunch spacing in the train [12,14,17]. Alternatively one can use an undulator, creating a THz free electron laser (FEL).…”

“…Such microbunching can be produced at the photocathode by means of laser microbunches spaced at subpicosecond intervals [7,8]. Alternatively one can start with a longer electron beam and perform bunch compression [9,10] and/or use a beam masking technique in conjunction with phase space manipulation systems, like an emittance exchanger [11,12] to produce required bunching. We propose to use the beam's self-wake action along with compression in a chicane to introduce THz content into the beam.…”